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Olfaction Expert Describes Passion for 'Nosing Around'

April 16, 2002

It's perhaps the most underappreciated of all our physical features--roundly resented for being too broad, too narrow, too pointy, too bumpy or too "pug." But to Dr. Stuart Firestein, associate professor of biology at Columbia University in New York, the nose--a model of sensory sophistication--is nothing to sniff at.

"It's the best chemical detector on the planet," he declared matter-of-factly to an audience of 150-plus at The Brain, the Body, and Aging, a conference sponsored by NIH in accordance with Brain Awareness Week. Firestein, who delved into the question of how we smell, as well as current trends in olfaction research, spoke on behalf of the National Institute on Deafness and Other Communication Disorders, which has funded his research for more than a decade. Brain Awareness Week is an international educational effort of the Dana Alliance for Brain Initiatives and its sponsoring partners, of which NIH is a member. The National Institute on Aging took the lead in this year's conference, held at the University of Maryland's Rockville campus on March 11 and 15.

"The nose does a lot more than just hold up our eyeglasses," Firestein remarked amiably to the crowd of primarily senior citizens, who also had listened to lectures on Alzheimer's disease, "senior moments," and macular degeneration that day. Although generally not crucial to one's day-to-day survival, our sense of smell plays a key role in the smelling and tasting of food, in sexual and social encounters, and in sensing environmental danger such as fires or gas leaks.

The inability to smell, or anosmia, can have a negative effect on a person's quality of life, Firestein said. For example, in an attempt to counteract the perceived blandness of food, individuals who can't smell may have the tendency to eat more sweet, salty and spicy fare--just the kinds of foods nutritionists tell us to steer clear of. They also may be ostracized socially for wearing too much perfume--or too little deodorant. Furthermore, not only are they at greater risk of not detecting certain environmental hazards, such as a gas leak in the home, but the realization of this fact can lead to psychological problems such as paranoia.

Odors--whether emanating from a sweet-smelling gardenia or a rank sweat sock--are volatile chemicals that can kill olfactory neurons. As a result, these neurons are replaced regularly throughout our lives. As we age, however, our ability to replace cells slows, which explains why so many elderly people lose their sensitivity to smell. Pollutants, head trauma, bacterial or viral infections, allergies or sinusitis, and genetic factors also can lead to a reduction in olfactory ability.

Firestein credits genomics--the study of an organism's complete genetic make-up--for generating some of the most exciting research findings in recent years regarding our ability to smell.

For example, when the mouse's 1,000 genes that actively code for olfactory receptors (another 300 genes are considered "pseudogenes," which means they may have been important at one time, but don't play a role anymore) were overlaid with the human's 350 genes (some 650 olfactory genes are pseudogenes), researchers discovered that the same area was covered, though in humans, one gene performed the work of three or four genes in mice. "That means that we can smell everything a mouse can, but that mice are able to discriminate more keenly between smells," said Firestein. "It also means that the mouse is a good model for studying smell in humans."

Currently, Firestein is studying the mouse to determine whether different genes are more active during certain periods of an organism's life, and "turned off" during others.

According to Firestein, understanding how we smell has many beneficial applications: from helping rescue workers cope with objectionable odors while searching for survivors, to developing a "stink bomb" so foul and enduring that it could be used to force a military foe out of hiding. In addition, if certain olfactory receptors are more likely to become depleted as we age, then perhaps a food additive could be developed to target other receptors--making food, and life, a whole lot more palatable for the hundreds of thousands of Americans with smell disorders.